Electrical heating system



Dec. 15, 1936.

J. c. SHARP 2,064,634

ELECTRICAL HEATING SYSTEM Filed Dt. 25', 1954 Fi .1. \5a\ /25 rse,

'S I5 16a 17a -nb 15a Joh r1 C. Sharp,

1S Attcneg:

Patented Dec. 175, 1936 PATENT OFFICE ELECTRICAL HEATING SYSTEM John C. Sharp, Oak Park, Il l., assignor to Edison General Electric Appliance Company,` Chicago, lll., a corporation of New York Application October 23, 1934, Serial No. 749,544

3 Claims.

This invention relates to electric heating system's, more'particularly to heating systems for electric coolringv appliances, such as electric ranges, and it has for its object the provision 5 of an improved system of thischaracterproviding various rates of heat generation. y

This invention is particularly applicable to heating systems for electric range surface units and the like, wherein a supply source is vused having two voltages, such as a three-wire source wherein the voltage between the two main wires is twice asgreat as that between each main wire and the neutral, for example, 230 volts between the main wires and 115 volts between each main wire and the neutral. Heretofore, in systems of this character, it has been the practice to use a heating unit having two heat generating resistance elements. These resistance elements are l connected to the supply source in such manner as to give three wattage combinations, which provide high, medium and low heats. In the systems of connections heretofore generally used, the ratios of the heats are, assuming high heat equal to one-medium one-half, and low onequarter heat. These ratios are not satisfactory in many cases in that low heat, which is ordinarily used just to maintain a boiling, temperature, usually has a somewhat higher wattage input th'an is necessary. This results in excessive evaporation and waste of heat.

Furthermore, in certain cases it is desirable to obtain a high wattage input, such as 900 watts, for rapid preheating, and a low wattage input,-,- as low as 100 watts-to maintain a boiling temperature. Heretoiore, a low wattage input has been obtained by providing an auxiliary resistance element for the heating unit formed of very fine wire. This element isfragile and has provento be unsatisfactory, especially when high 40 voltages, such as 230. are used.

This invention contemplates the provision of an improved heating system whereby relatively wide ratios are obtained between the high, low and mediumY heats in a simple, reliable and emcient manner, and with the use of two resistance elements.

In accordance with this invention, a heating unit is provided having two resistance elements. One resistance element is arranged to have a predetermined wattage input when' operated on .the maximum voltage between two main wires of the supply source, while the other is arranged to have a predetermined wattage input when' -operated on the reduced voltage between one of the 55 main wires and the neutral wire. The combined wattage inputs of the two resistance elements when thusoperated provides the high heat desiredl In order to obtain the medium heat, the two resistance elements are connected in parallel across one of the main wires and the neutral 5 wire, while low heat is obtained by connecting the high voltage rating resistance element across one of the main wires and the neutral.

For a more complete understanding of this invention, reference should be had to the accom- 10 panying drawing in which Fig. l is a diagrammatic view illustrating a heating system arranged in accordance with this invention, and illustrating diagrammatically switching means provided to control the connections between the 15 resistance elements of a heating unit and their supplyvsource; and Figs. 2, 3 and 4 are views similar to Fig. l, but illustrating the switching means in diiIerent controlling positions to provide different connections between the resistance elements and the supply source, whereby high,` medium and low heats are produced respectively.

Referring to the drawing, this invention has been shownin one form, as applied to an electric heating system for hot plates and the like of an 25 electric range, but.it is to be understood that the invention has other applications. As shown` in Fig. 1, the hotNplate i0shown diagrammatically, comprises two resistance elements Il and l2. 30`

The resistance elements Il and l2 -are provided with a suitable electrical supplysource I3 shown as a three-wire electrical supply source having two main wires Ila and IIb and a neutral wire lic. The voltage across the main 35 wires Ila and lib is double the voltage between either of the main wires lla, IIb, and the neutral wire lic. For example, the voltage between the main wires Ita. and I3b may be 230 volts, while the voltage between either of the main wires o Y and the neutral wire willy be 115 volts.

The resistance element Il is so arranged that when it is connected tov one of 'the main wires Ila, IIb and the neutral lic, it will take a predetermined wattage input, while the resistance 45 element I2 is so arranged that when it is con` nected to the two main wires ila and Hb it will take a predetermined wattage input. rFor L example, the resistance element ll when connected between one of the mainwires and the 50 neutral, that is, on the 115 volt source, will have a 500 watt input. while the resistance element I2 will be arranged so that when it isconnected across the two main wires on the 230 volt source, it will have an input of say 400 watts. As

pointed out previously, it is contemplated that when the two elements II and I2 are connected simultaneously to the supply source I3 so that the element II is connected to one of the main wires I3a, I3b and the neutral I3c, while the element I2 is connected to the two main wires I3a and I3b, the combined wattage input of the elements will provide a high rate of heat generation. As also pointed out, it is further contemplated that in order to obtain a medium heat the resistance element II will be connected, as before, to one of the outside wires I3a, I3b and the neutral |30, while in this case, the resistance I2 likewise will be connected across one of the main wires and the neutral in parallelv with the resistance II. In order to obtain low heat, the resistance element I2, which is designed to take a predetermined wattage input when operated across the high voltage source I3a, I3b, will be connected across one of the main wires I3a, I3b and the neutral I3c.

More specifically, in the specific example given wherein the voltage between the main wires I3a and |31) is 230 and that between either main Wire and the neutral I3c is 115, and where the resistance element II has a wattage input of 500 when connected to the 115 volt source, while the resistance element I2 when connected to the 230 volt source has a wattage input of 400, then when the two elements I I and I2 are connected respectively to these sources, they will take a combined input of 900 watts, which in this case provides the high heat condition of the heating unit I 0. When the two resistance elements II and I2 are connected in parallel across one of the main wires I3a, I3b and the neutral I3c, that is to the 115 volt source, they will take a wattage input of 600 watts, which is the medium heat generated by the heating unit I0, and when the high voltage resistance element I2 alone is connected to the lowvoltage source across one of the main wires I3a, I3b and the neutral I3c it will have a wattage input of 100 watts, which provides low heat in the unit ID. It will be observed, therefore, that the heating element I has-a very large ratio between the low heat wattage input of 100 watts and the 900 watts input for the high heat operation of the unit. It will also be observed that a very useful medium heat wattage input of 600 watts is provided.

The heating elements are controlled by means of a single multiple position manually operable control switch I 4. This switch may have any l fixed contacts Ia and I5b; the contactor I6 with fixed contacts I 6a and IBb; and the contactor I1 withA xed contacts IIa, I'Ib and IIc.

As shown in Fig. 1, when the switch is in its off position, neither one of the resistance elements II or I2 is connected with the supply source I3. However, when the switch is rotated to its high heat position (Fig. 2) by moving it a quarter turn in the clockwise direction from its oi position, the left hand end of the resistance element II will be connected to the lower main Wire IIb 'of the' supply source I3 through the contactor I5, while its right hand end will be connected to the neutral wire I3c through the contactor I6. In this position of the switch, the left-hand end of the resistance element I2 will be connected with the main wire I3b of the supply source through the contactor I5 and its other end with the main wire I3a through the contactor II. Thus, in the high heat position, the resistance element II is connected to the 115 volt source, while the resistance element I2 is connected to the 230 volt source. As pointed out previously, the wattage inputs of the two elements are thus combined so as to provide the high heat generation for the heating unit I0. When the switch is moved a quarter turn from its position shown in Fig. 2 to its position shown in Fig. 3, it will connect the elements II and I2 to the supply source I3 to provide the medium heat. In this position of the switch, the left-hand ends of both resistance elements II and I2 are connected to the main wire I3b of the supply source through the contactor I5, while the right-hand ends of these elements are connected to the neutral wire I3c by means of the contactors I6 and I'I respectively. In other words, the two elements II and I2 are connected in multiple across the 115 volt source. When the switch is moved a quarter turn from its position shown in Fig. 3 to.its low heat position shown in Fig. 4, the resistance element II is disconnected from the supply source, while the left-hand end of the resistance element I2 is connected to the main wire I 3b through the contactor I5 and its right hand end is connected to the neutral wire I3c through the contactor Il.

It is to be understood that the above figures with reference to the voltages of the supply source and the wattage inputs that the two elements Il and I2 have respectively when connected to the low and high voltages of the supply source are merely illustrative, and that the elements II and I2 may have any suitable wattage inputs when operated respectively on the low and high voltages of the supply source, and that these voltages may be varied. It is to be noted, however, that irrespective of the wattage inputs that these elements take when connected to the two sources, the ratio between the low wattage input for low heat and the high wattage input for high heat is materially increased over that obtained in the heating systems heretofore generally used. It is also to be noted that a medium heat wattage input intermediate these low and high heat inputs has been provided which is more useful than the medium heat wattage inputs heretofore provided.

It is also tobe understood that the resistance elements II and I2 may be supplied from two voltage sources of supply other than the threewire system I3 shown in the drawing; thus, for example, the elements may be supplied from a three-phase, four-wire system wherein the voltage between two of the main wires provides the high voltage source, while that between one of the main wires and the neutral provides thc low voltage source.

While I have shown a particular embodiment of my inventioz it will be understood of course that I do not wish to be limited thereto since many modications may be made, and I, therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States,jis:

l. An electrical heating system for a hot plate of an electric range and the like comprising a three-wire source having a relatively high voltage across two of said wires as compared with that across each of said two wires and the third wire, a single heat generating element for said hot plate comprising a pair of resistance elements, each having-but two terminals and one' arranged to take a predetermined wattage input when its two terminals are connected to said two wires and the other a predetermined wattage input when its two terminals are connected to one of said two wires and said third wire, a single multi-position switch controlling said resistance elements arranged in one positionto connect simultaneously the two terminals of said rst resistance element to said two wires and those of said second resistance element to one of said two wires and said third wire, whereby said predeterminediwattage inputs are combined to produce a high heat generation for said hot plate, and in another position to connect only the two terminals of said first resistance element to one of said two wires and said third wire to produce a low heat generation for said hot plate.

2. An electric heating system for a hot plate of an electric range and the like comprising an electrical supply source having a relatively high and a relatively low voltage, a single heat generating element for said hot plate comprising a pair of resistance elements, each having but two terminals and one having a rating to take a predetermined wattage input when its two terminals are connected to said high voltage source and the other having a rating to take a predetermined wattage input when its terminals are connected to said low voltage, a single multiposition switch controlling said heat generating element arranged in one position to connect simultaneously ,the two terminals of said rst resistance element to said supply source so that said high voltage is supplied to it and the two of said second resistance element to said supply source so that said low voltage is supplied to it,

whereby said predetermined wattage inputs of said elements are combined to provide a high heat for said hot plate, in another position to connect the two terminals of each resistance to said supply source so that said low voltage is applied to both of them simultaneously to provide a medium heat for said hot plate, and in still another position to connect only the two terminals of said first resistance element to said supply source so.that said low voltage is supplied to it to provide a low heat for said hot plate.

3. An electrical heating system for a hot plate and the like comprising a three-wire electrical supply source having two main wires and a neutral wire, the voltage between the main wires being relatively high as compared with that between each main wire and said neutral wire, an electrical heating element for said hot plate provided with a pair of resistance elements, each having but two terminals and one having a predetermined Wattage input when its two terminals are connected to said two main wires and the other a predetermined wattage input when its two terminals are Aconnected to one of said main wires and said neutral wire, and a single multi-position switch controlling saidlresistance elements arranged in one position to connect one terminal of each of said resistance elements to one of said main wires, the other' terminal of said -ilrst resistance element to the neutral wire and the other terminal of said second resistance element to the other main wire to effect a high heat condition in said hot plate, in another position to connect one terminal of each of said re-v sistance elements to one of said main wires and the other terminals of each of said elements to said neutral wire to effect a medium heat condition in said hot plate, and in still another position, to connect one terminal of said second v resistance element to one of said main wires and its other terminal to said neutral wire to effect a low heat condition in said hot plate, said first resistance element being disconnected from said supply' source in this position of said switch.

JoHN" c. SHARP; 

